1. Field of the Invention
This invention generally relates to a ship, in particular a deep-draft vessel configured for travel on the oceans or great lakes. Such a ship generally has a hull, and can be configured to have an engine disposed within the hull. A propeller shaft, connected to the engine at one end thereof, can then be disposed to pass through the hull of the ship into the surrounding water, at which end of the shaft at least one propeller can be mounted. With such a configuration, it is generally necessary to provide some sort of seal about the propeller shaft to seal out the surrounding water, and seal in any lubricants which may be disposed about the propeller shaft within the ship. Further, such a ship may be outfitted with two concentrically rotating propeller shafts, which rotate in opposite directions to one another. Such a configuration would therefore also generally need an additional seal between the two concentric shafts. In general, it is necessary to lubricate and cool the sealing surfaces of the individual seals, so that the useful life of the individual seals is prolonged, and the risk of failure of the seals is reduced.
2. Background Information
One type of seal which has been found to be useful for propeller shafts, is a lip seal, wherein the seals are circumferentially disposed about the propeller shafts, with a lip portion disposed in engagement with the outer surface of the propeller shaft.
Several types of lubricating systems are known for providing lubricating oil to the vicinity of the seal lips. However, in the lubrication systems, as disclosed by U.S. Pat. No. 4,793,773 and also by German Laid Open Patent Application No. 1,901,620 (which claims priority from a U.S. patent application filed on Feb. 6, 1993 having Ser. No. 703,323, the lubricating oil feed to the seals-does not take place by means of a separate forced feed lubrication, but only by means of the lubrication system for the shaft bearings, so that the lubricating oil gets to the seals only after passing the bearings, that is, essentially unpressurized.
To one skilled in the art, it becomes readily apparent that when such seals are subjected to extreme stresses, such a lubrication system is not capable of effectively lubricating and simultaneously cooling the sealing surfaces of all of the individual seals, so that the useful life of the individual seals can essentially be shortened, thereby increasing the danger of leaks or failure of the individual seals, and thus of the escape of lubricating oil into the surrounding water.
In addition, in seal arrangements for concentric propeller shafts, such as the arrangement as disclosed by German Laid Open Patent Application No. 1,901,620, a problem can arise as a result of the fluctuations of the clearance between the inner and outer shafts in the vicinity of the inner shaft seal. Thus, a correct seal can generally not be guaranteed, because either excessive pressure is applied to the seal lips fastened rigidly to the outer shaft, thus compressing the seal lips, or insufficient pressure is applied to the seal lips, thus adversely affecting the ability of the seal lips to seal out water, or seal in lubricants.